Example 5: North Sea Oil Valve

This is an arduous application involving the passage of slurries of sand, oil, water and gas. The ball valve is made in stainless steel, with a seat made in a similar material. Above all, you need to protect it from wear and seizure.

Entering details of the consultation

Enter this as before. Call the component a 'Ball Valve'

Choosing the type of contact

You will see a screen like this:

This time there is an engineering component (the seat) as the counterface and there is likely to abrasive product (sand) trapped between the rubbing surfaces.
You should select both the boxes and move on. The programme will follow the sequence shown in the bottom line on the facing page.

Choosing the substrate material

Select Stainless Steel.

Choosing the counterface material

Again, select 'Stainless Steel'. Call it a 'Seat'.

Entering the contact loading conditions

Tick Sliding, Surface Cyclic Loading and Solid Particle Erosion. All apply to this situation. No one of them is Dominant.

Entering more contact conditions

Wear is the issue here, not friction. But this is a Heavy Contact Loading situation, so mark it as such. By doing so, the programme will assess the problem as being one of High Stress Abrasive Wear and eliminate many of the thinner and softer coating options.
 

Specifying the hardness

Here, the computer needs some help. It has inserted a provisional figure of 200Hv (the substrate hardness) for your surface, but if you want maximum wear resistance under these very aggressive abrasive conditions you'll need to increase it. Consult the HELP screen; it advises a value of 1050Hv as a minimum figure for this situation. Type it in and move on.
 

Specifying the required surface finish

You need a good finish. Type in 0.2µ in all three boxes and tick yes to allow post finishing. Since you can finish it after coating, you can allow surface roughing prior to coating.
 

Selecting partial coating options

Select Defined areas must be coated.
 

Entering the operating temperature

It will run at temperatures up to 100oC. Enter the values. You Don't Care how hot you get the stainless steel ball during processing.
 

Specifying chemical contamination

Select Salt Water.
 

Requirements for mould release or food approval

Neither of these is applicable.
 

Entering the component dimensions

It is a 300mm dia ball. Enter the value in two of the boxes.
 

Describing the component's geometry

None of these apply.
 

Examining the results

 
Only the hardest and toughest of the thermally sprayed ceramics and cermets, as well as some of the hard chrome plates, can cope with this aggressive situation.
Try going back to the Hardness screen through the "Data" box and increasing your requirement to 1200Hv and then 1500Hv. Only a few of the sprayed coatings will then be applicable to provide the maximum possible wear resistance.
 

Poeton Industries Ltd. Head Office, Eastern Avenue, Gloucester GL4 3DN, England, UK   Tel: 01452 300500  Fax: 01452 500400
Production facilities in Cardif & Gloucester and in Wisconsin. USA.